Paging service providers (hereinafter "providers") implement paging systems to provide brief messages to paging service subscribers (hereinafter "subscribers"). FIG. 1 is a simplified diagram illustrative of a paging system 10. Generally, a person (i.e., the caller) who wishes to contact the subscriber may call the subscriber's pager telephone number using telephone 11 and initiate a page containing a brief message that is broadcast to the subscriber. The telephone call is routed through the publicly switched telephone network (PSTN) 12 to a paging terminal (PT) 13. The caller can then initiate a page, which PT 13 then provides to a number of paging stations (PSs) 14.sub.1 -14.sub.N to transmit the page in a broadcast fashion The paging system typically has a service area in which the subscriber can accurately receive the page. The subscriber then receives the page through a portable remote receiver unit (pager) 15, which receives pages and notifies the subscriber upon receipt of a page. Typically, a pager has a unique address that the pager searches for in the broadcasted pages to find pages intended for the subscriber. The subscriber would then generally keep the pager nearby during the times the subscriber wants to receive pages.
FIG. 2 is a block diagram illustrative of pager 15. Typically, pager 15 includes a battery 20 or other energy storage device to provide power to operate the circuitry of pager 15. A pager generally includes a central processing unit (CPU) 21 to execute software or firmware in operating the pager, a clock generator (CG) 22 to generate accurate clock signals used by CPU 21 and other circuitry, a memory 23 to store information, a display 24 (e.g., an LCD) to display alphanumeric messages, such as telephone numbers or short written messages), and a receiver 25 to receive pages broadcast by the paging system. Two-way pagers may include an input/output (I/O) device 26 (e.g., alphanumeric pushbuttons to input alphanumeric messages) and a transmitter 27 to send the message back to the PT 13. Digital voice pagers may include a voice synthesizer 28 or other conversion device used in converting a received voice page into an analog acoustic signal that the subscriber can hear. Two-way voice pagers may include a microphone for inputting voice messages to be transmitted back to the PT. Because battery 20 provides all of the power used by pager 15, power conservation becomes an important issue.
FIG. 3 is a diagram illustrative of cycle partitioning in an exemplary paging protocol. A paging protocol is typically partitioned into a number of cycles. As shown in FIG. 4, each cycle is partitioned into a number of frames. Typically, a frame would contain a batch of pages addressed to a large number of pagers. A frame would be partitioned into a number of segments, as shown in FIG. 5. A frame might start with a header synchronization (HS) segment, followed by a system information (SI) segment, followed by addresses and data. In particular, a first address (A1) and a first data (D1) portion would form a first page, while a second address (A2) and a second data (D2) portion would form a second page, and so on. In this type of partitioning, a pager would typically receive a large portion of the frame to determine if any of the addresses matched the address of that particular pager. If the pager finds its address in the group of received addresses, then the pager receives the corresponding data portion. It will be appreciated that the pager consumes a significant amount of power in receiving and processing these pages.
As mentioned above, reducing power consumption in a pager is an important concern because pagers are typically battery-powered and, thus, have a limited power supply. In addition to the power dissipated in receiving and processing pages, another significant source of power consumption in a pager is in initially "acquiring" a channel and a time slot in the channel. In acquisition, a pager generally has to scan through one or more channels for transmissions that the pager can recognize and then detect pages addressed to that particular pager. This process causes the pager to consume a relatively large amount of power. In addition, this process can be exacerbated in paging systems that use multiple protocols in a single channel and/or have several channels supporting a particular protocol. Further, the subscriber may travel out of the service area, which prevents the pager from detecting any recognized channels. Accordingly, there is a need for a paging system that reduces pager power dissipation in processing pages and acquiring channels.